SD card not readable in Catalina

Hi silverfox63,

Unplug the SD card, wait a moment, then re-insert it very quickly into the Mac.

1. Next, go to Disk Utility
2. Select "View" > "Show All Devices"
3. Look for the top, non indented, SD card.
4. Click Erase, and format accordingly.

If it still doesn't show up,

• Reset NVRAM: Reset NVRAM or PRAM on your Mac - Apple Support
• Reset SMC: How to reset the SMC of your Mac - Apple Support

Cheers,

Jack

What I've found recently are two things, both physical in nature:

First the SD cards wouldn't show up in two 2011 Macbook Airs, wiggling the card in the slot made them reappear, the conclusion being just dirty contacts.

Second, the now readable cards could not be written to and all showed up as no_write. The also could not be formatted regardless of the lock-switch position on the cards, or the speed of insertion as suggested elsewhere. I concluded a possible cause could be the lockswitch position sensor in the Macbook's card reader. Being hard to reach and clean I tried putting one or two pieces of tape over the entire lockswitch-channel on the card itself and to my surprise it worked, most of the time. Filling the gap in the lockswitch-channel and then taping it over appeared to do the trick.

Good luck.

If anybody knows how to clean this little switch, as it is probably just a little sticky, please advise.

I've noticed with some Macs you need to insert the card very quickly into the slot, otherwise it will not register. It also might need formatting, and the Mac might need some resets.

Cheers,

Jack